1. Field of the Invention
The present invention relates to apparatus and method for analysis of an electric power transmission link status, and more particularly apparatus and method for real-time analysis of an electric power transmission link status, which has a function of calculating and displaying thermal resistance and thermal capacity of environment around an installed electric power transmission link.
2. Description of the Related Art
The term ‘electric power transmission link’ used in this specification and appended claims is defined to include cables, joints and branches used for transmitting electric power from a supplier (e.g., a power generator, a transformer substation and a power distribution station) to a consumer (e.g., a transformer substation, a power distribution station and a final user such as a building or a house), and referred to as ‘a link’ hereinafter.
The link sensitively responds to the change of environment such as temperature around a spot where the link is buried or temporarily installed, so such a change of environment significantly affects on transmission capacity and stability of the link. Particularly, the transmission capacity and capacity of the link installed under the ground are seriously influenced by a thermal parameter, namely thermal resistance and thermal capacity. The electric power transmission of the link generates heat, and this heat causes moisture in the surrounding soil to be moved, thereby increasing the thermal resistance. The increase of thermal resistance caused by the work of the link limits the electric current acceptable to the link to an extreme level. Thus, operating the link without consciousness of the increase of thermal resistance may lead to a critical accident such as thermal breakdown or firing.
In the present, as disclosed in Korean Patent Laid-open Publication No. 2001-79444 or U.S. Pat. No. 6,167,525, there are some attempts to prevent such a critical accident. For example, after measuring temperature of the outer surface of the link or outside of the insulating material along the longitudinal direction of the link, the temperature of a conductor in the electric power transmission cable may be calculated and informed to an operator in real time on the basis of the measured values. In addition, an ampacity (or, a current carrying capacity) acceptable to the link may be calculated on the basis of the temperature of the conductor. The calculated values in both cases are used to prevent unexpected accidents. Here, when calculating the conductor temperature or the ampacity, the thermal resistance of the soil is conventionally set to a fixed value defined by the international standard, e.g. 1 K·m/W in the temperate regions.
However, thermal resistance and thermal capacity substantially have changing values according to soil or environment around the link or an operation condition of the link, and the conventional techniques are not capable of coping with the change of such external thermal parameters. In addition, though the techniques intend to take preventive measures against any critical accident by calculating the conductor temperature in real time, they are still insufficient for preventing the critical accidents caused by the change of thermal parameters since the conductor temperature is not measured from the conductor itself but calculated on the basis of an external temperature out of the link and the fixed thermal parameters defined regardless of the current conditions.
On the other hand, there is also a way of installing a sensor for directly measuring the thermal parameters of surroundings, particularly soil. However, since the link is too long, monitoring the entire length of the link is practically impossible.